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Heme B

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Heme B
Skeletal formula of heme B
Space-filling model of the heme B complex
Names
Other names Iron protoporphyrin IX,
protoheme IX
Identifiers
CAS Number
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.114.904 Edit this at Wikidata
MeSH Heme+b
PubChem CID
UNII
CompTox Dashboard (EPA)
InChI
  • InChI=1S/C34H34N4O4.Fe/c1-7-21-17(3)25-13-26-19(5)23(9-11-33(39)40)31(37-26)16-32-24(10-12-34(41)42)20(6)28(38-32)15-30-22(8-2)18(4)27(36-30)14-29(21)35-25;/h7-8,13-16H,1-2,9-12H2,3-6H3,(H4,35,36,37,38,39,40,41,42);/q;+2/p-2/b25-13-,26-13-,27-14-,28-15-,29-14-,30-15-,31-16-,32-16-;Key: KABFMIBPWCXCRK-RGGAHWMASA-L
  • InChI=1/C34H34N4O4.Fe/c1-7-21-17(3)25-13-26-19(5)23(9-11-33(39)40)31(37-26)16-32-24(10-12-34(41)42)20(6)28(38-32)15-30-22(8-2)18(4)27(36-30)14-29(21)35-25;/h7-8,13-16H,1-2,9-12H2,3-6H3,(H4,35,36,37,38,39,40,41,42);/q;+2/p-2/b25-13-,26-13-,27-14-,28-15-,29-14-,30-15-,31-16-,32-16-;/rC34H32FeN4O4/c1-7-21-17(3)25-13-29-20(6)24(10-12-34(42)43)32-16-28-23(9-11-33(40)41)18(4)26(37-28)14-31-22(8-2)19(5)30(15-27(21)36-25)38(31)35-39(29)32/h7-8,13-16H,1-2,9-12H2,3-6H3,(H,40,41)(H,42,43)/b25-13-,26-14-,27-15-,28-16-,29-13-,30-15-,31-14-,32-16-Key: KABFMIBPWCXCRK-SMDPYJEOBB
SMILES
  • OC(=O)CC/C6=C(\C)/C=3/N=C6/C=C2/C(/CCC(O)=O)=C(/C)\C1=C\C5=N\C(=C/c4n(N12)c(C=3)c(C=C)c4C)C(\C=C)=C5\C
  • OC(=O)CC/c6c(\C)c3n7c6cc2c(/CCC(O)=O)c(/C)c1cc5n8c(cc4n(78n12)c(c=3)c(C=C)c4c)c(\C=C)c5\C
Properties
Chemical formula C34H32O4N4Fe
Molar mass 616.487
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). checkY verify (what is  ?) Infobox references
Chemical compound

Heme B or haem B (also known as protoheme IX) is the most abundant heme. Hemoglobin and myoglobin are examples of oxygen transport proteins that contain heme B. The peroxidase family of enzymes also contain heme B. The COX-1 and COX-2 enzymes (cyclooxygenase) of recent fame, also contain heme B at one of two active sites.

Generally, heme B is attached to the surrounding protein matrix (known as the apoprotein) through a single coordination bond between the heme iron and an amino-acid side-chain.

Both hemoglobin and myoglobin have a coordination bond to an evolutionarily-conserved histidine, while nitric oxide synthase and cytochrome P450 have a coordination bond to an evolutionarily-conserved cysteine bound to the iron center of heme B.

Since the iron in heme B containing proteins is bound to the four nitrogens of the porphyrin (forming a plane) and a single electron donating atom of the protein, the iron is often in a pentacoordinate state. When oxygen or the toxic carbon monoxide is bound the iron becomes hexacoordinated. The correct structures of heme B and heme S were first elucidated by German chemist Hans Fischer.

Enzyme cofactors
Active forms
vitamins
non-vitamins
metal ions
Base forms
Types of tetrapyrroles
Bilanes
(Linear)
Phytobilins
Phycobilins
Macrocycle
Corrinoids
Porphyrins
Protoporphyrins
Phytoporphyrins
Reduced
porphyrins
Porphyrinogens
Chlorins
Bacteriochlorins
Isobacteriochlorins
Corphins

References

  1. Ogun, Aminat S.; Joy, Neena V.; Valentine, Menogh (2022), "Biochemistry, Heme Synthesis", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID 30726014, retrieved 2023-01-03
  2. Fischer, H.; Orth, H. (1934). Die Chemie des Pyrrols. Liepzig: Akademische Verlagsgesellschaft.
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